Scholastic
Study Jams! Area of a Triangle
Even though there is a wide variety of different triangles in the world, knowing a single equation allows us to find the area of each and every one of them. Follow along with this step-by-step presentation as Zoe clearly models how to...
Corbett Maths
Constructing SSS Triangles
Creating a triangles is as easy as 5, 6, 7. Using a ruler and compass to measure off lengths, a short video shows how to construct a triangle with three specific side lengths. The example creates a triangle with side lengths of 5 cm, 6...
Corbett Maths
Constructing ASA Triangles
The narrator of a short video explains the steps in constructing a triangle given the measure of two angles and the length of the side between the angles. The resource provides opportunities for pupils to practice the skill with two...
EngageNY
An Area Formula for Triangles
Use a triangle area formula that works when the height is unknown. The eighth installment in a 16-part series on trigonometry revisits the trigonometric triangle area formula that previously was shown to work with the acute triangles....
Charleston School District
Similar Triangles
Are they similar? The lesson provides an explanation of the angle-angle criterion for triangle similarity. Several problems allow the class to determine whether the two triangles with the given angle measures are similar or not.
CK-12 Foundation
Pythagorean Theorem for Solving Right Triangles: Solving the Triangle
Observe the change in the trigonometric ratios as angles vary. An interactive provides the values of trigonometric ratios for both acute angles in a right triangle. Pupils create a right triangle to match given criteria and find the...
Alabama Learning Exchange
Triangle Congruence with Rigid Motion
Combine transformations and triangle congruence in a single lesson. Scholars learn to view congruent triangles as a rigid transformation. Using triangle congruence criteria, learners identify congruent triangles and the rigid...
EngageNY
Congruence Criteria for Triangles—AAS and HL
How can you prove it? Guide classes through an exploration of two possible triangle congruence criteria: AAS and HL. Learners connect this criteria to those previous learned and also explore criteria that does not work. The lesson...
EngageNY
More About Similar Triangles
Determine whether two triangles are similar. The lesson presents opportunities for pupils to find the criterion needed to show that two triangles are similar. Scholars use the definition of similarity to find any missing side...
Curated OER
Alice in Fractalland
Take your class on a field trip to Fractalland where they'll learn all about number and shape patterns. Based on Disney's movie Alice in Wonderland, this resource takes young mathematicians on an adventure as they explore patterns in...
National Security Agency
Classifying Triangles
Building on young mathematicians' prior knowledge of three-sided shapes, this lesson series explores the defining characteristics of different types of triangles. Starting with a shared reading of the children's book The Greedy Triangle,...
CK-12 Foundation
Lengths of Sides in Isosceles Right Triangles: Paper Football
Fuse sports and geometry by having your class create paper footballs—that are actually isosceles right triangles! Scholars use an interactive to create an isosceles right triangle to model a paper football. From the information in the...
Flipped Math
Special Right Triangles I
Introduce a special relationship with right triangles. Learners discover the ratio of the sides in a 30-60-90 triangle. After watching several examples and seeing two different methods, pupils find unknown sides in triangles. Scholars...
CK-12 Foundation
Lengths of Triangle Sides Using the Pythagorean Theorem: Find the Missing Side
What is the relationship between the sides of a right triangle? Learners use an interactive to create models of right triangles and view the relationship between the lengths of the sides. They finish by using the Pythagorean Theorem to...
CK-12 Foundation
Relationships of Sides in 30-60-90 Right Triangles: Truck on a Mountain Road
Determine the change in elevation on a mountain road. Individuals use the interactive to simulate a truck driving up a mountain road with a 30-degree incline. They determine missing sides of a 30-60 right triangle to find horizontal and...
Flipped Math
Prove Triangles Similar
Show more than one way to prove similarity. Scholars learn three different methods to show two triangles are similar, Angle-Angle, Side-Side-Side, and Side-Angle-Side. Pupils practice applying these methods to determine whether two given...
CK-12 Foundation
Alternate Formula for the Area of a Triangle: Alternate Area of a Triangle
It's always nice to have a plan B. Pupils investigate an alternate formula for the area of a triangle that uses sine. A set of challenge questions shows how the new formula relates to the well-known formula of (1/2)bh.
CK-12 Foundation
Pascal's Triangle: Pyramid Blocks
Build a pyramid of sums. An interactive presents the first five rows of Pascal's Triangle as a pyramid. Pupils match missing entries in the pyramid and continue the pattern to determine entries of other rows. The learners use the entries...
McGraw Hill
The Wellness Triangle
Health is not simply the absence of disease or a one-dimensional notion, but is really a combination of physical, emotional, and social components. Discover the wellness triangle, which not only includes signs of health and ways to...
Corbett Maths
Pythagoras Rectangles and Isosceles Triangles
When does the Pythagorean Theorem come in handy? An intriguing video uses the Pythagorean Theorem to solve problems other than simply finding the length of a side of a right triangle. Pupils find the diagonal of a rectangle and the...
Digging Into Math
Classifying Triangles
Young mathematicians explore the world of three-sided shapes in this lesson on the different types of triangles. Starting with a general introduction to classification using Venn diagrams, children learn how to categorize triangles based...
Corbett Maths
Constructing SAS Triangles
Two sides and an angle ... a triangle it makes. Given the measure to two sides and the angle between them, the narrator of a short video shows how to draw a triangle with a ruler and protractor. Pupils use handouts to practice the newly...
Corbett Maths
Constructing Equilateral Triangles and 60 Degree Angles
Creating a 60-degree angle also creates an equilateral triangle. By watching the video, individuals learn the steps required to construct a 60-degree angle. The presentation shows that the process is the same for constructing an...
Corbett Maths
Showing a Triangle Is Right Angled
Determine whether it is right or not. Using the Pythagorean Theorem, the video shows how to determine whether a triangle is a right triangle. Pupils practice the skill in a few of the problems in the associated worksheets on the...
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